多功能孔压静力触探在基坑工程降水设计中的应用分析

针对南京长江四桥漫滩沉积土，分别进行了室内试验和多功能地震波孔压静力触探（SCPTU）原位测试，从SCPTU应用于场地复杂地层 的精细划分、长江漫滩沉积黏性土透水性能的评价和预测渗透系数kh 3个方面进行了详细分析，试验结果表明：综合利用 多功能SCPTU测试qt、fs、u2 3个参数可以对具有高度分层性和不均匀性的长江漫滩沉积土进行精确分层，对不同性质土 层界面、同一土层内透水或不透水夹层进行精确探测；利用SCPTU钻进过程中的孔压消散试验功能，可以对复杂的混合土层的透水性能进行评价；基于SCPTU的渗透系数kh预测值均具有一定的离散性，一般比室内试验结果高1～2个数量级，Burns & Mayne方法预测值可以作为工程初设阶段的参考值；SCPTU的应用为基坑工程降水设计提供了一种简便、快捷的新型技术手段。

Application of multifunctional SCPTU to dewatering design for deep excavation

Based on the laboratory and in situ seismic piezocone tests (SCPTU), comprehensive analyses of soils sampled from the Yangtze River floodplain at the Nanjing Fourth Bridge site were conducted, including the fine division of the soil layer, permeability evaluation of clayey soils and hydraulic conductivity prediction. It is shown that the measured parameters of SCPTU (qt、fs、u2) can be used effectively for profiling the highly layered and heterogeneous deposits in the Yangtze River floodplain, especially for identifying the soil interfaces, thin permeable or impermeable interlayers. Based on the dissipation of excess pore pressure in the process of SCPTU testing, the permeability of the complicated mixed soils can be evaluated. Based on SCPTU, the predicted kh values show significant discreteness. It is observed that the lab measured kh values are generally lower than those estimated from SCPTU within 1-2 orders of magnitude. The results from Burns & Mayne method (2002) can be used in the planning phase of civil engineering works. It is suggested that such an enhanced seismic piezocone test should be considered to be a new tool for the dewatering design of foundation pit engineering.